A number of types of reciprocating power tools are in use for various tasks, e.g. scrapers, saws, hammers or the like. Commonly such tools are hydraulically or pneumatically powered; however, such powering necessitates use of a noisy and bulky compressor or the like in conjunction with the tool itself, resulting in a limited range of utility for such tools. Further, such tools cannot easily or efficiently attain high speeds of reciprocation.
An alternative arrangement is to convert rotary movement provided by, for example, an electric motor into reciprocating movement of the tool bit. One means for achieving this conversion is to use the motor to drive the rotation of a cam bearing a cam track, and to provide the tool bit with a pair of cam followers, which are a close fit within the cam track. As the cam rotates the cam followers are driven forward and backward along the cam track, which is typically a sinusoidal cam track, so driving the tool bit forward and backward. Such arrangements are described in GB 2 219 958 A and WO 93/11910 by the same Inventor, the contents of which are incorporated herein by reference.
WO 01/60564 also by the same Inventor, the content of which is incorporated herein by reference, discloses a portable power tool, such as a hand-held marine growth removal scraper tool comprising a housing, a drive means and a mounting arrangement for a tool bit, wherein there is provided within the housing an output arrangement adapted to drive an output shaft in a reciprocal axial movement to drive the tool bit, and wherein the drive means is substantially sealed from external of the tool.
WO 02/14028 also by the same Inventor, the content of which is incorporated herein by reference, discloses a power tool comprising a housing, a rotary drive means, a cylinder cam having a cam track extending around a circumferential surface thereof, cam follower means adapted to run in said cam track, and a mounting arrangement for a tool bit, one of the cam and the cam follower means being driven by the drive means, and the mounting arrangement being associated with one of the cam and the cam follower means, such that actuation of the rotary drive means drives reciprocal movement of the mounting arrangement; and wherein at least part of the cam track is in the form of a wave having an amplitude and a wavelength, the wave providing a forward throw section and a rearward throw section which in use drive the mounting arrangement respectively forward and rearward, at least one of the forward throw section or rearward throw section imparting a greater forward or rearward acceleration respectively to the mounting arrangement than that imparted by a sinusoidal cam track of equivalent amplitude and wavelength.
A number of problems have been identified in the prior art. For example, when a tool is operated in particularly robust uses, e.g. marine hull scraping, it has been found desirable to seek to provide an improved tool. This is required in order to seek to ensure appropriate efficient functionality of the tool, e.g. removal of marine debris or encrustations, preferably without damaging the underlying substrate, e.g. hull.
Further, the pair of cam followers comprise pins which, e.g. due to repeated cyclic use, may become fatigued and liable to failure.
Yet further, the pair of cam followers and cam track of the prior art are difficult to adapt to many desirable cyclic (throw/return) motions.
It is an object of at least one embodiment of at least one aspect of the present invention to obviate or at least mitigate one or more problems and/or disadvantages in the prior art.
It is an object of at least one embodiment of at least one aspect of the present invention to provide an improved tool, e.g. a power tool, hand-held power tool, and/or scraper tool, e.g. marine tool such as an anti-fouling tool.